Image scanners are commonly used in offices or homes for scanning objects such as documents or photographs and processing the image of the objects into digital forms.
In addition to the function of scanning the documents or photographs, the functions of scanning slides and films become necessary.
The light source required for scanning the regular documents is positioned at the same side as the optical scanning module which is in the lower housing of the scanner. Whereas, for a purpose of scanning the slides and films, an upper light source is necessary.
In order to scan the opaque objects such as paper sheets, documents or photographs, the scanner should be operated in a reflective mode. In the reflective mode, the light emitted by the light source positioned at the same side as the optical scanning module and in the lower housing of the scanner is projected onto the surface of the opaque object. The light reflected from the opaque object is then transmitted into an image sensor of the optical scanning module. Whereas, for scanning the transparent objects such as slides or films, the scanner should be operated in a transmissive mode. Since the light emitted by the light source in the lower housing of the scanner fails to be reflected from the transparent object to the optical scanning module, the light emitted by the upper light source positioned at opposite side to the optical scanning module penetrates through the transparent object to be scanned, and then received by the image sensor of the optical scanning module.
In a case that the functions of scanning both opaque and transparent objects are provided, the scanner has a separate illuminator plate. When the scanner is operated in the reflective mode, the illuminator plate is detached from the scanner because the illuminator plate is not required at that moment. Whereas, when the scanner is operated in the transmissive mode, the illuminator plate is coupled to the scanner at the position where the upper cover is previously coupled.
Since the illuminator plate is an additional accessory of the scanner, the illuminator plate is detached from the scanner in most situations. In other words, if the illuminator plate and the scanner are separately stored, the probability of losing the illuminator plate is increased. Under this circumstance, the scanner fails to be operated in the transmissive mode.
For solving these problems, a transmissive scanner is disclosed in U.S. Pat. No. 6,417,937, which is referred hereinafter as '937 patent.
Referring to FIG. 1, a schematic view of the transmissive scanner described in the '937 patent is illustrated. The scanner 100 of the '937 patent has an automatic paper feeder 240. Specially, an upper light source 250 is disposed within the automatic paper feeder 240. Since the upper light source 250 is combined with the automatic paper feeder 240, the upper light source can be employed whenever the scanner is operated in the transmissive mode.
This '937 patent, however, still has some drawbacks. For example, the transmissive scanner has a holder for supporting the slides or films in position. Generally, the holder is arranged in the vicinity of the upper light source. As is described in the '937 patent, the holder is disposed on the automatic paper feeder 240. For scanning the slides or films, the automatic paper feeder 240 should be lifted up, the slides or films are then supported on the holder of the automatic paper feeder 240, and afterwards the automatic paper feeder 240 are placed on a glass platform. Since the automatic paper feeder is weighty, it is troublesome and labored to repeatedly uplift/lay down the automatic paper feeder to scan the transparent objects.
Furthermore, for uplifting the automatic paper feeder, the automatic paper feeder is pivotally mounted onto the main body of the scanner via a pivotal structure. Since this pivotal structure is larger than that in a situation when no automatic paper feeder is used, the gap between the automatic paper feeder and the glass platform is increased when the glass platform is covered by the automatic paper feeder. If the gap is greater than the depth of field of the image sensor, the image quality is impaired.
In views of the above-described disadvantages resulted from the prior art, the applicant keeps on carving unflaggingly to develop an image scanner having an illuminator plate according to the present invention through wholehearted experience and research.